@@ -2172,7 +2172,7 @@ unlock:
return err;
}
-static bool fs_fully_visible(struct file_system_type *fs_type);
+static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags);
/*
* create a new mount for userspace and request it to be added into the
@@ -2206,7 +2206,7 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
}
if (type->fs_flags & FS_USERNS_VISIBLE) {
- if (!fs_fully_visible(type))
+ if (!fs_fully_visible(type, &mnt_flags))
return -EPERM;
}
}
@@ -3029,9 +3029,10 @@ bool current_chrooted(void)
return chrooted;
}
-static bool fs_fully_visible(struct file_system_type *type)
+static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
{
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+ int new_flags = *new_mnt_flags;
struct mount *mnt;
bool visible = false;
@@ -3050,6 +3051,19 @@ static bool fs_fully_visible(struct file_system_type *type)
if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
continue;
+ /* Verify the mount flags are equal to or more permissive
+ * than the proposed new mount.
+ */
+ if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
+ !(new_flags & MNT_READONLY))
+ continue;
+ if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
+ !(new_flags & MNT_NODEV))
+ continue;
+ if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
+ ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
+ continue;
+
/* This mount is not fully visible if there are any child mounts
* that cover anything except for empty directories.
*/
@@ -3060,6 +3074,10 @@ static bool fs_fully_visible(struct file_system_type *type)
if (inode->i_nlink > 2)
goto next;
}
+ /* Preserve the locked attributes */
+ *new_mnt_flags |= mnt->mnt.mnt_flags & (MNT_LOCK_READONLY | \
+ MNT_LOCK_NODEV | \
+ MNT_LOCK_ATIME);
visible = true;
goto found;
next: ;
This is a note to let you know that I have just added a patch titled mnt: Modify fs_fully_visible to deal with locked ro nodev and atime to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt15. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From f923f4144d7f8d0c829196881bf6ef83d4671a47 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" <ebiederm@xmission.com> Date: Fri, 8 May 2015 23:49:47 -0500 Subject: mnt: Modify fs_fully_visible to deal with locked ro nodev and atime commit 8c6cf9cc829fcd0b179b59f7fe288941d0e31108 upstream. Ignore an existing mount if the locked readonly, nodev or atime attributes are less permissive than the desired attributes of the new mount. On success ensure the new mount locks all of the same readonly, nodev and atime attributes as the old mount. The nosuid and noexec attributes are not checked here as this change is destined for stable and enforcing those attributes causes a regression in lxc and libvirt-lxc where those applications will not start and there are no known executables on sysfs or proc and no known way to create exectuables without code modifications Fixes: e51db73532955 ("userns: Better restrictions on when proc and sysfs can be mounted") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- fs/namespace.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-)